Suspension apparatus for washing machine and washing machine having the same

ABSTRACT

A suspension apparatus for a washing machine comprises: a pivot mounted to a casing; a damper cap mounted to an outer tub installed in the casing; a connection rod having the pivot and the damper cap at both ends thereof; and an elastic means formed in the damper cap, wherein a contact area decreasing portion for reducing a contact area on the surface of the pivot is formed on the pivot. Under this configuration, vibration or noise transmitted to a mounting surface for the pivot is reduced.

RELATED APPLICATION

The present invention relates to subject matter contained in priority Korean Application No. 10-2007-0076582, filed on Jul. 30, 2007, which is herein expressly incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a washing machine, and more particularly, to a suspension apparatus for a washing machine capable of reducing vibration or noise transmitted to a body of a washing machine from an outer tub, by forming a contact area decreasing portion on either an upper pivot or a mounting surface for the upper pivot so as to decrease a contact area therebetween, and thereby allowing lubricant deposited onto the contact area decreasing portion to stay for a long time, and a washing machine having the same.

2. Description of the Background Art

Generally, a washing machine serves to wash laundry by using a softening process by detergent, a frictional process by water stream occurring as washing blades rotate, an impact process by washing blades, etc. By using a motor as a main driving force, the washing machine performs a washing process, a rinsing process, and a dehydrating process so as to wash laundry with using detergent and water. The washing machine comprises a motor serving as a driving unit, a mechanical part for transmitting energy to laundry, a controller for controlling washing processes, a water supply unit for supplying water, and a water drain unit for discharging water.

The washing machine is largely divided into a cylinder type, an agitator type, and a pulsator type according to washing methods.

According to the agitator type, an agitator protruding from the center of an inner tub with a wing shape is rotated in right and left directions thus to wash laundry. According to the pulsator type, laundry is washed by using turbulent stream occurring as a disc-shaped pulsator is rotated. According to the cylinder type, water, detergent, and laundry are put into a drum having a plurality of protrusions, and then are rotated with a low speed in a horizontal axis, thereby washing laundry by an impact occurring as the laundry is lifted and dropped by the protrusions.

FIG. 1 is a schematic sectional view of a washing machine in accordance with the related art, FIG. 2 is a schematic sectional view of a suspension apparatus for a washing machine in accordance with the related art, and FIG. 3 is an enlarged sectional view of ‘A’ of FIG. 2.

Referring to FIG. 1, a washing machine 1 comprises a body or a casing 10 that forms appearance; an outer tub 12 mounted in the casing 10; an inner tub 13 mounted in the outer tub 12; a suspension apparatus 20 or suspensions each having one end connected to an upper inner circumferential surface of the body or the casing 10, having another end connected to a lower outer circumferential surface of the outer tub 12, and configured to support the outer tub 12; and a driving unit 15 disposed below the outer tub 12, and configured to drive the inner tub 13.

Referring to FIG. 2, each of the suspensions 20 comprises a damper cap 22 installed below the outer tub 12; a connection rod 21 having one end penetrating the damper cap 22, and another end disposed at an upper pivot 25 mounted to the casing 10; a damper spring 23 mounted in the damper cap 22, and configured to absorb vibration from the outer tub 12; and a damper base 24 installed at a lower opening of the damper cap 22, and configured to support the connection rod 21 or the damper spring 23. Here, the upper pivot 25 for supporting an upper end of the connection rod 21 is installed at the casing 10 or a suspension mounting portion 14 of the casing 10 or the body. And, a mounting hole 14 a for inserting the upper pivot 25 is formed at the suspension mounting portion 14.

According to a basic vibration reducing mechanism, vibration occurring from the inner tub 13 is reduced by a viscous damping force occurring as air is discharged through an air hole (not shown) of the damper cap 22, and by a frictional damping force occurring as the damper cap 22 and the damper base 24 come into friction with each other. Here, excessive vibration or amplitude is reduced by a viscous damping force.

Vibration occurring from the inner tub 13 or the outer tub 12 is transmitted to the casing 10 through the suspension 20. In order to reduce vibration or noise transmitted to the casing 10 and smoothly support the upper pivot 25, as shown in FIG. 3, a lubricant 16 such as grease is deposited between the suspension mounting portion 14 and a mounting surface for the upper pivot 25.

However, when the suspension 20 is severely moved due to excessive vibration, the lubricant 16 disposed between the upper pivot 25 and the suspension mounting portion 14 plane-contacting each other is discharged out. Accordingly, the lubricant 16 does not perform its function well.

Furthermore, since there is no medium material for absorbing vibration or noise between the upper pivot 25 and the suspension mounting portion 14, a contact area between the upper pivot 25 and the suspension mounting portion 14 is increased. Accordingly, most of vibration or noise occurring from the outer tub 12, etc. is transmitted to the casing 11, thereby increasing entire noise or vibration.

An air gap which allows a reciprocation of the washing machine is formed between the damper cap 22 and the damper base 24. If the washing machine 1 is used by approximately 1000 cycles, a clearance of the air gap is increased to allow a large amount of air to leak through the air gap. This causes a viscous damping force to be greatly lowered, thereby not reducing excessive vibration.

SUMMARY OF THE INVENTION

Therefore, it is a first object of the present invention to provide a suspension apparatus for a washing machine capable of reducing vibration or noise transmitted to a casing by decreasing a contact area between a pivot and a suspension mounting portion of a casing for mounting the pivot, by forming a contact area decreasing portion on either the pivot or the suspension mounting portion, and a washing machine having the same.

It is a second object of the present invention to provide a suspension apparatus for a washing machine capable of allowing a lubricant deposited onto a contact area decreasing portion to stay for a long time without being discharged therefrom even when being severely moved, by concavely forming the contact area decreasing portion at either a pivot or a suspension mounting portion of a casing for mounting the pivot, and a washing machine having the same.

It is a third object of the present invention to provide a suspension apparatus for a washing machine capable of having a constant abrasion of a damper base in a circumferential direction and capable of enhancing reliability, by using an extension spring consecutively contacting the damper base in a circumferential direction, and a washing machine having the same.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a suspension apparatus for a washing machine, comprising: a pivot mounted to a casing; a damper cap mounted to an outer tub installed in the casing; a connection rod having the pivot and the damper cap at both ends thereof; and an elastic means formed in the damper cap, wherein a contact area decreasing portion for reducing a contact area on the surface of the pivot is formed on the pivot.

Under this configuration, a contact area of the pivot to the casing is reduced, and vibration or noise transmitted to the casing due to a direct contact between the pivot and the casing is reduced.

Here, the contact area decreasing portion is a dimple concavely formed on the surface of the pivot, or a groove formed on the surface of the pivot. That is, owing to a concaved dimple or groove, a contact area of the pivot to the casing is reduced.

A lubricant may be deposited to the contact area decreasing portion. Once a lubricant is deposited to the contact area decreasing portion, i.e., the concaved dimple or groove, the lubricant is not discharged out. Also, when the suspension apparatus is severely moved at the time of excessive vibration, a lubricating process can be stably performed, and a function for preventing noise/vibration can be effectively performed.

A damper base sliding along an inner surface of the damper cap, and configured to support one end of the connection rod is further formed at one end of the damper cap. Below the damper base, may be mounted an extension spring for uniformly maintaining an air gap between the damper base and the damper cap, and thereby increasing a viscous damping force by air leaked through the air gap.

Here, the extension spring consecutively contacts a lower side surface of the damper base. The reason is in order to maintain a constant abrasion of the damper cap and the damper base in a circumferential direction, to reduce a lowering of a viscous damping force due to non-uniform increase of an air gap, and to prolong a life-span of the suspension apparatus.

A base cap for reducing a leakage amount of air inside the damper cap may be further mounted below the damper cap. Accordingly, even if the air gap between the damper cap and the damper base is non-uniformly increased, a lowering of a viscous damping force can be prevented.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is also provided a washing machine having a suspension apparatus, the washing machine comprising a casing, an outer tub installed in the casing, and a suspension apparatus installed between the casing and the outer tub, wherein the suspension apparatus comprises: a pivot mounted to the casing; a damper cap mounted to the outer tub installed in the casing; a connection rod having the pivot and the damper cap at both ends thereof; and an elastic means formed in the damper cap, wherein a contact area decreasing portion for reducing a contact area between the pivot and the casing is formed on the surface of either the casing, or the pivot.

The contact area decreasing portion may be implemented as a concaved dimple or groove, and a lubricant may be deposited to the contact area decreasing portion. Once a lubricant is deposited to the contact area decreasing portion, the lubricant is not discharged out. Also, when the suspension apparatus is severely moved at the time of excessive vibration, a lubricating process can be stably performed, and a function for preventing noise/vibration can be effectively performed.

A base cap for reducing a leakage amount of air inside the damper cap may be further mounted below the damper cap. An air hole for a viscous damping may be formed at either the damper cap or the base cap, or at both of them.

A damper base sliding along an inner surface of the damper cap, and configured to support one end of the connection rod is further formed at one end of the damper cap. Below the damper base, may be mounted an extension spring for uniformly maintaining an air gap between the damper base and the damper cap, and thereby increasing a viscous damping force by air leaked through the air gap.

Under this configuration, a lowering of a viscous damping force due to air inside the damper cap can be reduced.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

In the drawings:

FIG. 1 is a schematic sectional view of a washing machine in accordance with the related art;

FIG. 2 is a schematic sectional view of a suspension apparatus for a washing machine in accordance with the related art;

FIG. 3 is an enlarged sectional view of ‘A’ of FIG. 2;

FIGS. 4A to 4C are views showing a pivot of a suspension apparatus according to the present invention;

FIG. 5 is a sectional view showing a state that the pivot of FIG. 4 is mounted to a washing machine;

FIG. 6 is a sectional view of a lower configuration of the suspension apparatus of FIG. 4;

FIGS. 7A to 7C are views respectively showing an extension spring of the suspension apparatus of FIG. 4;

FIG. 8 is a sectional view showing a modification example of a lower configuration of the suspension apparatus of FIG. 6; and

FIG. 9 is an experimental graph showing each noise occurring from the conventional suspension apparatus and the suspension apparatus of FIG. 4 according to a frequency.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

Hereinafter, the configuration and operation of a suspension apparatus for a washing machine according to one embodiment of the present invention will be explained in more detail with reference to the attached drawings.

Explanation for well-known configurations or functions will be omitted. And the same reference numerals will be given to the same parts as those of the aforementioned configurations, and their detailed explanation will be omitted.

FIGS. 4A to 4C are views showing an upper pivot of a suspension apparatus according to the present invention, and FIG. 5 is a sectional view of the upper pivot of FIG. 4 showing a mounted state to a washing machine.

Referring to FIG. 4A, an upper end of a connection rod 210 of a suspension apparatus 200 according to the present invention is exposed to an upper surface of a pivot 270 by penetrating the pivot 270. The upper end of the connection rod 210 undergoes a caulking process, or is implemented as an additional member such as nuts so as not to be separated from the pivot 270.

When viewed from the top, the pivot 270 has an approximate circle shape. A coupling hole 271 for the connection rod 210 is formed at a central portion of the pivot 270. A connection rod supporting portion 272 for stably supporting the connection rod 210 is extendingly formed at a part where the coupling hole 271 is formed, in a downward direction along the connection rod 210.

A part where the connection rod supporting portion 272 starts to extend is extended in a circumferential direction, thereby being integrally formed with a mounting portion 273 having a similar shape to a top. Here, a lower surface of the mounting portion 273 comes in contact with the casing 10 (refer to FIG. 1) of the washing machine 10 (refer to FIG. 1) or the body, thereby mounting the pivot 270.

A contact area decreasing portion 274 is formed on a lower surface of the mounting portion 273. The contact area decreasing portion 274 serves to decrease a contact area between a lower surface of the mounting portion 273 and the surface of the casing 10.

The contact area decreasing portion 274 is concavely formed on a lower surface of the mounting portion 273, and is preferably implemented as a dimple or a groove on the surface of a golf ball.

FIG. 4B is a bottom view of the pivot 270 having a plurality of contact area decreasing portions 274 in the form of dimples, and FIG. 4C is a bottom view of a pivot 270′ having a plurality of contact area decreasing portions 274′ in the form of concaved grooves.

Here, the contact area decreasing portions 274 and 274′ may be concavely formed on each lower surface of the mounting portions 273 and 273′, and may be also protruding from each lower surface of the mounting portions 273 and 273′.

Regardless of a concaved shape or a convex shape, the contact area decreasing portions 274 and 274′ may have any shape to decrease a contact area between each surface of the mounting portions 273 and 273′ and the casing 10.

FIG. 5 is a view showing a state that the pivot 270 of the suspension apparatus 200 is mounted to a suspension mounting portion 140 of the casing. The suspension mounting portion 140 is a part of the casing 10 (refer to FIG. 1) or the body. Preferably, the suspension mounting portion 140 is respectively formed at four corners of the washing machine 1. A mounting hole for inserting the pivot 270 is formed at the suspension mounting portion 140.

A lubricant 160 such as grease is interposed between the suspension mounting portion 140 and the pivot 270 mounted to the mounting hole of the suspension mounting portion 140.

Preferably, a sufficient amount of the lubricant 160 is deposited between the pivot 270 and the suspension mounting portion 140.

The lubricant 160 is filled in the contact area decreasing portions 274 and 274′, thereby performing a lubricating process so as to decrease a friction between the suspension mounting portion 140 and the mounting portion 273 of the pivot 270.

The lubricant 160 may also perform a vibration absorbing function or a vibration preventing function, which prevents or reduces vibration or noise occurring along the connection rod 210 from being transmitted to the casing 10 or the suspension mounting portion 140 via the pivot 270. More concretely, vibration or noise transmitted to the casing 10 where the suspension mounting portion 140 is formed, or to the body has a lowered intensity via the lubricant 160 deposited between the pivot 270 and the suspension mounting portion 140, and then is transmitted to the casing 10, etc. Accordingly, noise due to vibration of the case 10, etc. is considerably reduced.

Furthermore, even if the suspension apparatus 200 is severely moved due to vibration of outer tub 12 (refer to FIG. 1) in an excessive vibration state such as an initial stage for dehydration, the lubricant can stably stay at the contact area decreasing portions 274 and 274′, and the lubricant 160 deposited between the pivot 270 and the suspension mounting portion 140 is prevented from being discharged therefrom.

The contact area decreasing portions 274 and 274′ may be formed not only on the pivot 270 of the suspension 120, but also on the suspension mounting portion 140 or the casing 10. That is, the contact area decreasing portions 274 and 274′ may be formed on the surface of either the suspension mounting portion 140, or the mounting portion 273 of the pivot 270.

Hereinafter, a lower part of the suspension apparatus, that is, a part connected to the outer tub 12 will be explained in more detail.

FIG. 6 is a sectional view of a lower configuration of the suspension apparatus of FIG. 4, FIGS. 7A to 7C are views respectively showing an extension spring of the suspension apparatus of FIG. 4, and FIG. 8 is a sectional view showing a modification example of a lower configuration of the suspension apparatus of FIG. 6.

As shown in FIG. 6, the suspension apparatus 200 for a washing machine according to the present invention comprises: a connection rod 210; a damper cap 220 having one end of the connection rod 210 penetratingly formed thereat; a damper spring 230 installed in the damper cap 220; a damper base 240 configured to support one end of the connection rod 210 penetratingly installed at the damper cap 220; extension springs 260 mounted to a lower side of the damper base 240; and a base cap 250 mounted to a lower opening of the damper cap 220.

An upper portion of the damper cap 220 is upwardly extending like a bottle neck, and the upwardly extending portion encompasses the connection rod 210.

The connection rod 210 is positioned inside the damper cap 220 via a through hole 222 formed at the upper portion of the damper cap 220. One end of the through hole 222 is protruding to inside of the damper cap 220, thereby constituting a connection rod supporting portion 223 that encompasses and supports the connection rod 210.

One end of the connection rod 210 is fixed to a connection rod fixing portion 241 protruding from an upper surface of the damper base 240 by a certain height. Preferably, the connection rod fixing portion 241 is formed to have a certain height so as to stably support the connection rod 210.

A plurality of protrusions 242 are formed on an outer circumferential surface of the connection rod fixing portion 241. The plurality of protrusions 242 are forcibly inserted into an inner circumferential surface of the damper spring 230, thereby stably supporting the damper spring 230.

A lower end of the damper spring 230 is supported by the protrusions 242 on the surface of the connection rod fixing portion 241, and an upper end of the damper spring 230 is supported by a spring supporting portion 224 formed on an inner surface of the damper cap 220.

At an initial state, i.e., at a state that the washing machine is not provided with washing water or laundry therein, the damper spring 230 preferably maintains a compressed state, and the damper base 240 for supporting the damper spring 230 is positioned at an inner side of a lower end of the damper cap 220. The reason is as follows. Once laundry or washing water is introduced into the inner tub 13 (refer to FIG. 1), the damper spring 230 is extended due to a weight of the laundry or washing water, and the damper base 240 moves to a lower side of the damper cap 220. Here, if the damper base 240 is positioned at the end of the damper cap 220, laundry, etc. is introduced into the inner tub 13, and the damper base 240 may be completely separated from the damper cap 220.

Here, the damper spring 230 is preferably a compression coil spring, but is not limited thereto. As the damper spring 230, any elastic means having an elastic restoration force and configured to absorb or attenuate vibration may be used. For example, a rubber member may be used to connect one end of the connection rod 210 and the connection rod fixing portion 241 of the damper base 240. Also, a rubber pillar (not shown) having a cavity therein may be used as the damper spring 230. When the damper spring 230 is used as an elastic means, one end of the connection rod 210 disposed in the damper cap 220 is preferably disposed inside the damper spring 230.

An air hole 221 is formed at an upper portion of the damper cap 220, through which a viscous damping process due to air inside the damper cap 220 is performed. Between an inner surface of the damper cap 220 and an outermost circumference of the damper base 240, a minute air gap (not shown) is formed. A frictional damping process occurs through the air gap.

The base cap 250 may be mounted to a lower opening of the damper cap 220. The base cap 250 is coupled to the damper cap 220 by a hook (not shown) formed at the damper cap 220 with receiving the damper base 240 therein. In order to ensure a sealed state inside the damper cap 220, the damper cap 220 and the base cap 250 may be coupled to each other by forming a screw thread at a coupling portion therebetween.

The damper base 240 will be explained in more detail with reference to FIG. 5.

The connection rod fixing portion 241 connected to one end of the connection rod 210 is formed above the damper base 240, and the plurality of protrusions 242 are provided on an outer circumferential surface of the connection rod fixing portion 241. A spring supporting portion 243 is integrally formed below the connection rod fixing portion 241. Preferably, the spring supporting portion 243 is formed in a wide disc shape so as to sufficiently support the damper spring 230.

A skirt portion 244 having an area wider than that of the spring supporting portion 243 is integrally formed below the spring supporting portion 243. Here, the skirt portion 244 is in a thin cylindrical shape having a predetermined height, and an air gap is formed between an outer surface of the skirt portion 244 and an inner surface of the damper cap 220.

Referring to FIG. 7A, a plurality of slits (not shown) are formed at the skirt portion 244 in a height direction, and an extension spring 260 is mounted to an inner surface of the skirt portion 244. Here, in order to prevent the extension spring 260 from being separated from the skirt portion 244, a concaved groove (not shown) or stopping jaws 245 are formed on an inner surface of the skirt portion 244.

Since the extension spring 260 is mounted to the skirt portion 244 with a diameter decreased than the original diameter, it has an elastic restoration force to restore the original diameter. Due to the elastic restoration force, the edge of the damper base 240 is extended to an inner surface of the damper cap 220. That is, the skirt portion 244 is pushed to the damper cap 220 thus to be extended.

Here, the skirt portion 244 can have a large extension degree by being provided with the plurality of slits in a height direction thereof. The skirt portion 244 can be outwardly extended even by the extension spring 260 having a small elastic restoration force.

Either the stopping jaws 245 or the slits, or both the stopping jaws 245 and the slits can be formed with consideration of the size of the damper base 240, or an elastic force of the extension spring 260, etc.

The extension spring 260 has to be provided with a consecutive circumference.

When viewed from the front, the extension spring 260 is in a ring shape having a consecutive circumference (refer to FIG. 7B), whereas when viewed from the side, the extension spring 260 has some parts overlapping each other in a longitudinal direction (refer to FIG. 7C). That is, the extension spring 260 is wound so that both ends thereof can overlap each other by a predetermined length.

Here, curved portions 260 a and 260 b are formed at both ends of the extension spring 260 toward the center of the extension spring 260. The curved portions 260 a and 260 b are used to mount the extension spring 260 to the damper base 240. When the curved portions 260 a and 260 b are pressed at both sides, a diameter of one side of the extension spring 260 is decreased to allow the extension spring 260 to be easily mounted to the damper base 240. Then, when the curved portions 260 a and 260 b are released, the extension spring 260 is restored to the original state. At the same time, the skirt portion 243 is outwardly extended.

As shown in FIG. 7A, the extension spring 260 consecutively contacts lower side surfaces of the damper base 240, i.e., the skirt portion 244, due to its consecutive circumference. That is, all parts of the extension spring 260 come in contact with the skirt portion 244. Accordingly, an air gap between the damper cap 220 and the damper base 240 is uniformly maintained in a circumferential direction of the extension spring 260, thereby preventing non-uniform clearance of the air gap.

As the extension spring 260 having a consecutive circumference is used, the skirt portion 244 of the damper base 240 is prevented from being flatly abraded even when coming into friction with an inner surface of the damper cap 220.

The suspension apparatus 200′ of FIG. 8 is different from the suspension apparatus 200 of FIG. 6 in that an air hole 251 is formed at a base cap 250′.

According to the suspension apparatus 200 of FIG. 6, the base cap 250 is mounted to a lower side of the damper cap 220, but an air hole is not formed at the base cap 250. This allows air leakage through the air gap to be prevented, but causes air inside the damper cap 220 to have a difficulty in being discharged out, which can not reduce excessive vibration. In order to solve this problem, the air hole 251 may be formed at the base cap 250′.

The air hole 251 of the base cap 250′ is formed approximately at a lower surface of the suspension apparatus 200′. Accordingly, even if a lubricant such as grease deposited on the damper cap 220 flows down, the air hole 251 is not blocked.

When the air hole 251 is formed at the base cap 250′, it is preferable not to form the air hole 221 blocked by a lubricant at the damper cap 220. However, when a sufficient viscous damping force can not be obtained from the air hole 251 of the base cap 250′, it is effective to form the air hole 221 at the damper cap 220. In this case, in order to prevent the air hole 221 of the damper cap 220 from being blocked by a lubricant such as grease, the air hole 221 is formed at an upper side.

In order to reduce excessive vibration of the washing machine by using a viscous damping force occurring from air leakage, either the air hole 221 of the damper cap 220 or the air hole 251 of the base cap 250′, or both of them may be formed. This selection has to be performed in the aspect of vibration with consideration of a capacity of the washing machine, a rotation speed of the inner tube at the time of a dehydration process, etc.

By using each of the suspension apparatuses 200 and 200′, the air gap between the damper cap 220 and each of the dampers bases 250 and 250′ can be constantly maintained. This causes a viscous damping force by air leaked through the air gap to be increased.

FIG. 9 is an experimental graph showing each noise according to a frequency, the noise occurring from the conventional suspension apparatus and the suspension apparatus of FIG. 4.

Referring to FIG. 9, a horizontal axis of the graph denotes a frequency (Hz), and a vertical axis of the graph shows noise (dB) transmitted to the suspension mounting portion 140 or the casing 10.

When comparing each noise occurring at a middle frequency (‘B’ of FIG. 9), noise occurring from the suspension apparatuses 200 and 200′ having the contact area decreasing portions 274 and 274′ according to the present invention is considerably less than noise occurring from the conventional suspension apparatus.

So far, the present applicant explained about the suspension apparatus applied to a washing machine, but the suspension apparatus may also be applied to various fields such as a washing machine compatible with a drier, a dryer, or a combined washing system.

The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teachings can be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments.

As the present features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims. 

1. A suspension apparatus for a washing machine, comprising: a pivot mounted to a casing; a damper cap mounted to an outer tub installed in the casing; a connection rod having the pivot and the damper cap at both ends thereof; and an elastic means formed in the damper cap, wherein a contact area decreasing portion for reducing a contact area on the surface of the pivot is formed on the pivot.
 2. The apparatus of claim 1, wherein the elastic means is a damper spring.
 3. The apparatus of claim 1, wherein the contact area decreasing portion includes dimples concavely formed on the surface of the pivot.
 4. The apparatus of claim 1, wherein the contact area decreasing portion includes a groove formed on the surface of the pivot.
 5. The apparatus of claim 1, wherein a lubricant is deposited to the contact area decreasing portion.
 6. The apparatus of claim 5, wherein a damper base sliding along an inner surface of the damper cap and supporting one end of the connection rod is provided in the damper cap, wherein below the damper base, mounted is an extension spring for uniformly maintaining an air gap between the damper base and the damper cap, and thereby increasing a viscous damping force by air leaked through the air gap.
 7. The apparatus of claim 6, wherein the extension spring consecutively contacts a lower side surface of the damper base.
 8. The apparatus of claim 7, further comprising a base cap mounted to a lower side of the damper cap, and configured to reduce a leakage amount of air inside the damper cap.
 9. A washing machine having a suspension apparatus, the washing machine comprising a casing, an outer tub installed in the casing, and a suspension apparatus installed between the casing and the outer tub, wherein the suspension apparatus comprises: a pivot mounted to the casing; a damper cap mounted to the outer tub installed in the casing; a connection rod having the pivot and the damper cap at both ends thereof; and an elastic means formed in the damper cap, wherein a contact area decreasing portion for reducing a contact area between the pivot and the casing is formed on the surface of either the casing, or the pivot.
 10. The washing machine of claim 9, wherein the elastic means is a damper spring.
 11. The washing machine of claim 9, wherein the contact area decreasing portion includes concaved dimples or grooves.
 12. The washing machine of claim 9, wherein a lubricant is deposited to the contact area decreasing portion.
 13. The washing machine of claim 12, wherein the suspension apparatus further comprises a base cap mounted to a lower side of the damper cap, and configured to reduce a leakage amount of air inside the damper cap.
 14. The washing machine of claim 13, wherein an air hole for a viscous damping is formed at either the damper cap or the base cap.
 15. The washing machine of claim 12, wherein a damper base sliding along an inner surface of the damper cap and supporting one end of the connection rod is provided in the damper cap, wherein below the damper base, mounted is an extension spring for uniformly maintaining an air gap between the damper base and the damper cap, and thereby increasing a viscous damping force by air leaked through the air gap. 